The invention relates to a method for manufacturing an implant consisting of a preferably adsorbable carrier material containing medically active agents such as pharmaceutical agents, antibiotics, cytostatics, hormones or the like.
In orthopedic operations, infections of the bone tissue (osteomyelitis) are common, which must be treated with antibiotics. Frequently, antibiotics administered intravenously or orally are without lasting therapeutic effect, even if the pathogen is susceptible. The reason is that the infected sectors are difficult to reach when the blood circulation is poor, when there is scar formation or sclerosis, and when there are membrane-like structures around the bacterial colonies which the antibiotics have difficulty penetrating. For that reason, it is inevitable that to control infections by means of intravenous or oral antibiotics, high doses must be administered on a long-term basis. However, there are limits to large doses due to the systemic side effects that may occur.
When infections occur in the bone tissue, a supplementary surgical intervention is therefore often necessary, in which all infected tissue sections are removed. Surgical debridement inevitably results in bone defects. To compensate for those, bone transplants are used, and this can cause numerous problems. Thus, bone transplants are primarily avital and therefore an ideal breeding ground for renewed bacterial invasion. As a rule, these bone transplants are therefore introduced only in a subsequent step, after the infection has been controlled. Otherwise there is a danger of sequestering the infection and making it persist.
It has therefore already been suggested to apply antibiotics locally in the infected area, but this has resulted in only partial success.
Local instillations are either too short in their effect or they require the application of time-consuming supply systems. At present, practically the only clinical method used consists of antibiotics carriers in the form of polymethylmetacrylate which are incubated with gentamycin. Other antibiotics can hardly be combined with such a carrier, which is reason enough for their limited use. The tissue levels reached are higher than with an intravenous or oral administration of antibiotics, but they are usually still insufficient for eliminating resistant germs. A substantial disadvantage of such antibiotics carriers is that they must be removed again after the patient has been at rest for a few days. To eliminate this disadvantage, some adsorbable implants have been developed very recently which consist of collagen sponges of animal origin, soaked in gentamycin. So far, this method cannot be used with other antibiotics, and such implants are also effective for a few days only.
In other forms of treatment, it is necessary that the implants deliver no or not only locally applied antibiotics, but also other medically active agents. Thus, transplants used to fill bone defects usually possess no osteoinductive potency, i.e. there is no stimulation for bone formation. For that reason, the defects cannot be induced to regenerate themselves. These transplants act only as spacers along which new endogenous tissue is supposed to form. It therefore seems useful to add factors which will stimulate bone regeneration. Some of these have already been identified, and some can even be produced by means of gene technology. However, problems persist in clinical applications, since such substances cannot be applied in a high-enough concentration and not long enough in the required place of activity.
In surgery involving malignant tumours, a high local concentration of cytostatics is desirable in certain cases. In such cases, it is particularly necessary to avoid systemic effects, since the resulting damage to organs can sometimes become life-threatening.
In the case of other active agents, too (hormones, pharmaceutical agents), it is sometimes desirable to produce either a locally limited or a long-term and continuous effect. These goals can be achieved through the implantation of suitable carriers with the desired active agent.